1 files changed, 40 insertions, 18 deletions

diff --git a/main.ha b/main.ha
index 8051da4..e3e9332 100644
--- a/main.ha
+++ b/main.ha
@@ -9,6 +9,7 @@ use sdl2;
 
 def SCALE: int = 20;
 def CLOCKSPEED: int = 600;
+def VOLUME: i16 = 3000;
 
 def SCREEN_WIDTH: size = 64;
 def SCREEN_HEIGHT: size = 32;
@@ -70,20 +71,6 @@ fn chip8() state = {
 	return state;
 };
 
-fn reset(state: *state) void = {
-	state.display = [false...];
-	state.keys = [false...];
-	state.stack = [0...];
-	state.SP = 0;
-	state.PC = START_ADDR;
-	state.V = [0...];
-	state.I = 0;
-	state.DT = 0;
-	state.ST = 0;
-
-	state.mem[..FONT_SIZE] = FONT[..];
-};
-
 fn instruction(opcode: u16) inst = inst {
 	op = opcode,
 	X = (opcode >> 8): u8 & 0x0F,
@@ -365,14 +352,15 @@ fn execute_instruction(state: *state, inst: inst, random: *random::random) void
 	};
 };
 
-fn tick_timers(state: *state) void = {
+fn tick_timers(state: *state, audio_device: SDL_AudioDeviceID) void = {
 	if (state.DT > 0)
 		state.DT -= 1;
 
 	if (state.ST > 0) {
-		// BEEP
-
 		state.ST -= 1;
+		SDL_PauseAudioDevice(audio_device, 0);
+	} else {
+		SDL_PauseAudioDevice(audio_device, 1);
 	};
 };
 
@@ -415,6 +403,22 @@ fn update_screen(state: *state, renderer: *sdl2::SDL_Renderer) (void | sdl2::err
 	sdl2::SDL_RenderPresent(renderer);
 };
 
+fn audio_callback(userdata: nullable *opaque, stream: *u8, len_: int) void = {
+	let stream: []i16 = *(&types::slice {
+		data = stream: *[*]i16,
+		length = len_: size / 2,
+		capacity = 0
+	}: *[]i16);
+
+	let sample_index = 0;
+	const half_square_wave_period = 44100 / 440 / 2;
+
+	for (let i = 0; i < len_ / 2; i += 1) {
+		stream[i] = if ((sample_index / half_square_wave_period) % 2 == 0) -VOLUME else VOLUME;
+		sample_index += 1;
+	};
+};
+
 fn run() (void | fs::error | io::error | sdl2::error) = {
 	if (len(os::args) < 2) {
 		fmt::fatalf("Usage: {} <rom>", os::args[0]);
@@ -440,6 +444,24 @@ fn run() (void | fs::error | io::error | sdl2::error) = {
 	let renderer = sdl2::SDL_CreateRenderer(window, -1, sdl2::SDL_RendererFlags::ACCELERATED)?;
 	defer sdl2::SDL_DestroyRenderer(renderer);
 
+	const want_spec = SDL_AudioSpec {
+		freq = 44100,
+		format = AUDIO_S16LSB,
+		channels = 1,
+		samples = 512,
+		callback = &audio_callback,
+		userdata = null,
+		...
+	};
+
+	let have_spec = SDL_AudioSpec {
+		callback = &audio_callback,
+		...
+	};
+
+	let dev = SDL_OpenAudioDevice(null, 0, &want_spec, &have_spec, 0)?;
+	defer SDL_CloseAudioDevice(dev);
+
 	sdl2::SDL_SetRenderDrawColor(renderer, 0x00, 0x00, 0x00, 0xFF)?;
 	sdl2::SDL_RenderClear(renderer)?;
 
@@ -551,7 +573,7 @@ fn run() (void | fs::error | io::error | sdl2::error) = {
 			chip8.draw = false;
 		};
 
-		tick_timers(&chip8);
+		tick_timers(&chip8, dev);
 	};
 };